Gnome 3 automatic execution of a script that needs network

Question

my old father is using ubuntu-gnome. He has no static ip address. In order to perform remote administration, I need to know his ip. I was using dyndns free account (configuration in the adsl modem), but this will stop working in a couple of days.

I would like to run a script each time he logs in to publish his ip on my website. I have tried to put a script on the boot, but the network is not available. It seems that it is gnome 3 that starts the network, but I do not know much about gnome 3.

How should I do to have my script run automatically as soon as the network is available ?

Answer 1

One possible non-elegant solution for this is to put your script in his cron to run every X minutes :)

Looking to mine /etc/NetworkManager/ looks like there is a folder dispatcher.d that I think it'll do what you want. Just experiment with a bash/perl/python w/e script in there set the permission appropriately. You can find the UUID in the system-connections/ folder. More information is available in man networkmanager.

EDIT: Look what I found: https://askubuntu.com/questions/13963/call-script-after-connecting-to-a-wireless-network. Seems like this is exactly what you want.

Answer 2

The easiest way is to use another dynamic DNS service. I used to use my own. You could also put curl or wget command to cron or create a systemd service that will call that command periodically. As a target you would have to use your machine with a web server where you can see the IP in your logs.

It is not Gnome that connects the network, it is a system service called NetworkManager. It tries to connect at boot if possible. In some cases it waits for wireless signal, in other cases it waits for a user password. I recently verified that in Fedora, NetworkManager properly implements the systemd's network-online.target but it may have yet to be fixed in other distributions, see the upstream bug report.

https://bugzilla.gnome.org/show_bug.cgi?id=728965

If you want to run a system service just after boot, you need to use:

[Unit]
...
Wants=network-online.target
After=network-online.target

You could also just run a script that calls nm-online at the beginning to wait for the network connectivity if you can expect the connectivity to come up in reasonable time, otherwise it times out. Such a script can be run from any environment including a user session.

And, as noted already, you can put a script into /etc/NetworkManager/dispatcher.d that will be called on any network configuration change and such a script can then filter connection up events and start the notification script.